DWR简单 实现单向聊天【文章三：业务层、控制层、bean】 功能登录显示登录用户【无数据库操作】
聊天业务类 主要业务 源代码如下：

package com.dwr;

import java.util.Date;
import java.util.HashMap;
import java.util.Map;
import java.util.Map.Entry;

import javax.servlet.http.HttpSession;

import org.directwebremoting.Browser;
import org.directwebremoting.ScriptBuffer;
import org.directwebremoting.ScriptSession;
import org.directwebremoting.ScriptSessions;
import org.directwebremoting.WebContextFactory;

import com.vo.User;

public class ChatDwr {
	public ChatDwr() {
		System.out.println("实例化");
		
 	}

	// sessionId和User对象
	public static Map<String, User> map = new HashMap<String, User>();
     
	// 登陆
	public boolean login(String username) {
		// session
		HttpSession session = WebContextFactory.get().getSession();
		// 键同，值不同（注销，put）
		// 键不同，值同（则在别处登陆,提示)
		// 键不同，值不同(新用户,put)
		//activeReverseAjaxEnable
		for (Entry<String, User> user : map.entrySet()) {
			String sid = user.getKey();
			String name = user.getValue().getName();
			if (name.equalsIgnoreCase(username) && !sid.equals(session.getId()))
				return true;//在别处登陆
			else if (username.equals("") && sid.equals(session.getId())) {
				map.remove(sid);
				break;
			}
		}
		// 保存用户
		ScriptSession ss = WebContextFactory.get().getScriptSession();
		if (username.length() > 0) {
			map.put(session.getId(), new User(ss.getId(),username));
			ss.setAttribute("username", username);
		}
		// 添加数据到用户列表
		Browser.withAllSessions(new Runnable() {

			public void run() {
				ScriptSessions.addFunctionCall("addUser", map.values());
			}
		});
        session.setAttribute("username", username);
		return false;
	}

	
	// 发送消息
	public boolean sendMsg(
		final String toId,	final String toName, final String msg) {
		final HttpSession session = WebContextFactory.get().getSession();
		final String from = (String) session.getAttribute("username");
		if (from==null || from.equals(toName))
			return false;
		Browser.withSession(toId, new Runnable() {

			public void run() {
				ScriptBuffer buff = new ScriptBuffer();
				buff.appendCall("recv", from, toName, msg, new Date());
				ScriptSession ss = Browser.getTargetSessions().iterator()
						.next();
				ss.addScript(buff);
				

			}
		});

		return true;
	}

	

	

}

--------------------------- 聊天业控制类 源代码如下：

package com.servlets;

import java.io.IOException;
import java.util.Collection;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

import org.directwebremoting.Browser;
import org.directwebremoting.ScriptSession;
import org.directwebremoting.ScriptSessions;
import org.directwebremoting.ServerContextFactory;
import org.directwebremoting.WebContextFactory;

import com.dwr.ChatDwr;

public class ExitGameServlet extends HttpServlet {

	public void service(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		final HttpSession session = request.getSession(false);
		if (session != null) {

			Browser.withAllSessions(new Runnable() {
				public void run() {
					
					System.out.println("来了");
					ChatDwr.map.remove(session.getId());
					session.invalidate();
					ScriptSessions.addFunctionCall("addUser", ChatDwr.map
							.values());

				}
			});

		}

	}

}

------------------------ 聊天vo类 源代码如下：

package com.vo;

public class User {
	
	private String id;  //scriptSessionId
	private String name;
	
	
	private String sid; //sessionId

	public String getId() {
		return id;
	}

	public void setId(String id) {
		this.id = id;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public User(String id, String name) {
		super();
		this.id = id;
		this.name = name;
	}

	public User() {
		super